Fluid supported rotor



Patented May 9, 1961 FLUID SUPPoRTED RoToR Elmer Fred Macks, Vermilion,Ohio, assigner, by direct and mesne assignments, to Air-Glide, Inc.,Cleveland, Ohio, a corporation Filed Jan. 28, 1958, Ser. No. 714,454

23 Claims. (Cl. S10-90) This invention relates to dynamoelectric devicesand more particularly to a dynamoelectric device having relativelyrotatable rotor and stator elements in which the rotor is totallysupported on a film of fluid when the device is in operation,

This application is a continuation in part of United States patentapplication Number 558,676 tiled January 12, 1956, by Elmer Fred Macksunder the title of Fluid Supported Rotor, which application has beenabandoned in favor of this application. This application is also acontinuation in part of United States patent application Number 643,666filed March 4, 1957, by Elmer Fred Macks under the title of AirSupported Rotor, now United States Patent No. 2,889,474, issued June 2,1959. Additional patent applications which present related, butindependent, inventions are Serial Number 577,828 filed April 12, 1956,under the title of Dynamoelectric Device With Fluid Supported Rotor, nowUnited States Patent No. 2,937,295 issued May 17, 1960, Serial Number578,536, led April 16, 1956, under the title of Fluid Dynamic Device,now United States Patent No. 2,916,642 issued December 8, 1959, SerialNumber 580,- 133 led April 23, 1956, under the title of Fluid SupportedRotor and United States application Number 700,651 filed December 4,1957, under the title of Dynarnoelectric Device, now United StatesPatent No. 2,928,960 issued March l5, 1960.

This invention is directed to dynamoelectric devices wherein the rotoris totally supported radially on a lm of fluid, which film is preferablyan air lm generated upon relative rotation of the rotor and stator. Theuid in such iilm is supplied by fluid which is ambient to thedynamoelectric device.

It has been discovered that if a smooth cylindrically contoured surfaceis provided in a stator, and a complemental smooth cylindricallycontoured surface is provided on a rotor, the rotor may be supported inthe stator for free, substantially frictionless rotation even with airambient to the motor as the lubricant. This is achieved by providing aprecision running t between the cylindrically contoured surfaces. As theelements are relatively rotated, a load carrying fluid film is producedbetween the elements and the rotor is totally supported radially on suchfluid lm in spaced relationship with the stator.

Rotors and armatures are ordinarily provided with shafts or slides toguide their motion during rotation or translation. Dynamoelectricmachines which are required .to operate for long periods present abearing problem since continuous lubrication is required to preventstructural failure. The cost of producing a machine is materiallyaifected by the bearing since close tolerances must be met in producingthe bearing mounts in proper align,

ment. Also, bearing material-lubricant combinations of adequate qualityfor long continuous use are necessarily expensive.

Accordingly, one of the principal objects of this invention is toprovide a new and novel dynamoelectric device of simple and inexpensiveconstruction and a device which, at the same time, has a long life andan increased eliiciency.

Another object of the invention is to provide a novel and improveddynamoelectric machine which has a single film of ambient fluiddeveloped in a fluid lm producing region located between complementalsurfaces on the rotor and stator, and developed upon relative rotationof the rotor and stator.

Another object of the invention is to provide a novel and improveddynamoelectric machine in which the rotating member is totally supportedradially on a ilm of gas, supplied by the gas ambient to the machine, topermit the rotor to rotate about its center of mass as opposed to itsgeometric axis.

Still another object of the invention is to provide a machine in whichthe outer surface of the rotor and the inner surface of the stator forma hydrodynamic lm therebetween of the fluid ambient to the machine.

A further object of this invention is to provide a machine in which theouter surface of the rotor and the inner surface of the stator form agas load carrying film or pneumodynamic lm therebetween of the fluidambient to the machine.

An additional object of this invention is to provide a machine in whicha gas lm of the gas ambient to the machine is formed between the outersurface of the rotor and the inner surface of a non-magnetic sleeve.

A still further object of the invention is to provide a machine in whichan inner surface on the rotatable element confronts an outer surface onthe stationary element with the geometric tolerance and surface iinishesbeing such that a pneumodynamic load carrying lm of the ambient gas suchas air is formed between the surfaces, and the rotating element issupported out of contact with the stationary element during relativerotation.

Yet another object of the invention is to provide a dynamoelectricmachine in which the rotor is totally supported on a film of airsupplied by the ambient atmosphere to provide a small, light, quietmachine at low production costs.

Still another object of the invention is to provide a novel and improvedmachine made in accordance with the foregoing in which the rotor istotally supported radially on a film of ambient air to provide anefcient maintenance free machine which is eiciently operable in a widerange of temperature conditions and with a very wide speed range.

A further object of the invention is to provide an odorlessdynamoelectric machine which has a high eiiiciency, an extremely longlife and an ambient air supported rotor which will coast for longperiods of time and operate even though only very crudely balanced ascompared with prior known constructions.

These listed objects will outline the invention, but other objects and afuller understanding of the invention may be had by referring to thefollowing description and claims, taken in conjunction with theaccompanying drawing, in which:

Figure 1 is a sectional view of a dynamoelectric device in which a loadcarrying fluid dynamic lrn is developed to hold the rotor and statorelements in spaced relationship;

Figure 2 is a sectional View of a dynamoelectric device similar to thedevice of Figure l wherein a sleeve is carried by one of the relativelyrotating elements;

Figure 3 is a sectional view of an electric motor for verticaloperation;

Figure 4 is a sectional view of the device of Figure V3 as seen from theplane indicated by the line 4 4 of Figure 3; and,

Figures 5 through 10 are sectional views of dynamo- Y'disposed in anyother direction.

electric machines each disclosing an alternate construction embodyingthe principles of this invention.

Referring to the drawing and to Figure l in particular, thedynamoelectric device disclosed may be either a motor or a generator inwhich a rotor 10 is an armature. The rotor Iy has a shaft 12 fixed to itas its geometric center. A stator 14, including the usual pole pieces,at least partially, surrounds the rotor 10. The stator 14 is providedwith a set of windings 16 which produce'the magnetic effects in the polepieces of the stator.

The absence of conventional bearings requires that the rotor and stator14, as an assembly, function as vthe bearing elements. It is alsoconsidered desirable to use the ambient fluid in which the motoroperates as the lubricant. In most instances air is available, but anyliquid or gas can be used. The use of air as a lubricant is preferredboth because of its availability and because of its superior operatingcharacteristics in many applications. The use of air is accomplished bydeveloping a pneumodynamic load carrying lilm of air between therelatively rotating parts. The load carrying iilm has pressurecharacteristics which are suicient to support the load.

The film is produced when the geometric tolerance and surface conditionsare held within certain limitations which will subsequently be describedin more detail. These conditions, as applied to the embodiments includedherein, affect in particular the surface finish, clearance, taper andout-of-round. These conditions also vary with the operating conditionssuch as speed and temperature and with the viscosity of the iluid whichis being used as the lubricant. A surface Vfinish is required to be inthe order of 16 microinch R.M.S. or smoother with a liquid as theambient fluid. The taper which is allowable between the surfaces with aliquid as the ambient uid is limited to the order of 0.0003 inch perinch of length. In the fluid film region designated by the letter R inFigure l, the radial clearance between the `confronting surfaces whenthey are concentric is limited to a ratio having a range within thelimits of 0.000050 to 0.003 inch per inch of diameter. For convenience,reference is made to rotor surface diameter in the claims. However,because of the high ratio between the diameter and the clearance, eithersurface may be used as a reference.

The clearance ratio generally increases with both an increase in theviscosity of the ambient uid and with a decrease in diameter. With airor gas as the lubricant the preferred radial clearance is between0.000050 to 0.0005 inch per inch of diameter, this clearance ratiogenerally increasing with a decrease in diameter. The clearance varieswidely depending on operating variables such as the speed of rotation.For satisfactory over-all performance with air or gas as the lubricantthe out-ofround tolerance of the confronting surfaces is held withinapproximately 0.0001 Vinch per inch of diameter and total taper is heldwithin one-quarter the radial clearance.

A dynamoelectric machine constructed with the previ- Vously outlinedcharacteristics operates with the rotor out of contact with the stator.Air or other gases, as well as fluids, will maintain the deviceoperative indefinitely since there is no contact between the relativelyrotating surfaces. The shaft 12 functions to transmit torque from themotor. The Vrotor is positioned axially by the magnetic eld or by anexternal device connected to the motor drive shaft 12. The rotor istotally supported on the load-carrying hydrodynamic film of fluidgenerated in the region ,R when there is relative rotation between therotor 10 and the stator 14. This total support is radially speaking, andit is present whether the rotation is about a horizontal axis as shown,or about an axis The influence of the magnetic eld of the stator isrelied upon to hold the rotor in position axiallyspeaking when the motoris in operation in a generally horizontal position. Therefore, the rotoris held totally supported by the film of uid. Thrust means may beprovided for devices wherein the axis of rotation approaches a verticaland to limit axis shifting of the rotor when the eld is inactivated. Thethrust means will subsequently be described in more detail. Theperformance of dynamoelectric machines made in accordance with thisinvention is outstanding. in the case of fractional horsepower inductionmotors, for example, it has been found that an eliiciency increase of 25percent may be achieved. All noise, other than transformer noise, iscompletely eliminated, since there is no contact of the moving parts inany direction even with ambient air as the only lubricant.

With air or gas as lubricant another outstanding advantage of theinvention is believed to reside in the unitary bearing concept. In allcases a single load-carrying film offers several unexpected and highlydesirable results.

In the case of alternating current dynamoelectric machines, a phenomenonhas been discovered which materially enhances the operation of thesemachines and therefore serves to contribute to the outstanding resultsachieved. Since the rotor is free to shift in any direction against thepressure of the load-carrying fluid film `and against the resistence ofthe magnetic field, the rotor in an alternating current device tends toreciprocate up and down in a very minute fashion at twice linefrequency. VThis reciprocation against the load-carrying film has theeffect of increasing the pressure of the lm and therefore increasing theload-carrying capacity of the film. The single fluid film associatedwith the unitary bearing conceptV enhances the inherent ability of analternating current dynamoelectric device to more fully utilize thesqueeze-film increase in load-carrying capacity.

Also the construction of these dynamoelectric machines with a singleload-carrying gas film is such that in many instances the rotor ispermitted to rotate about its own center of mass rather than itsgeometric center. Thus, vibration is reduced substantially and in manycases balancing of the rotating assembly may be eliminated.

Fulther, bearing stability is inherently enhanced by operation within analternating current magnetic iield. Normally, at high speeds and highclearance ratios bearing whirl Vdevelops in pneumodynamic film devicescausing vibration which ultimately leads to failure. The squeeze-filmaction of the alternating current device greatly extends the operatingspeed and clearance ratio range of unitary pneumodynamic support indynamoelectric equipment. This increase in the ratio range alsocontributes to the decrease in the need for balancing discussed above.

A further contribution of the unitary pneumody-namic supportedconstruction is the elimination of many alignment problems whileinherently maintaining the air gap with a high degree of concentricity.

In Figure 2 a dynamoelectric machine is disclosed in which a sleeve 18is carried in the stator I4. This sleeve is formed from a nonmagneticmaterial such as bronze or a plastic material such as a cast epoxy. Thesleeve also allows formation of a continuous surface throughout thecircumference of the bore. However, lthe sleeve 1S need not becontinuous around the circumference, but may extend only partiallyaround Vthe circumference, for example, the lower half.

The motor of Figure 3 is adapted for operation with the rotor 10 in aposition with the axis of rotation vertical. The Weight of the rotor t0is supported axially as well as radially. An end plate 20 is mounted onthe end of the stator 14, the surface of the plate confronting thesurface on the end of the rotor iti to form fa hydro'dynamic iilmtherebetween which operates as a thrust bearing.

The end of the rotor 10 is modified asillustrated in Figure 4 to obtainthe load supporting film. Either Ythe rotor end or the thrust plate maybe modied as indicated be low while the mating surface is iiat andsmooth. The surfaces 24 are below the plane of the segments 22 and rims23 a distance of 0.000020 to 0.002 as required by the unit load to besupported, the ambient fluid, and the speed of rotation. The recesses 24do not extend to the outer or inner peripheries thereby reducing endleakage by means of rims 23 from the hydrodynamic (film and increasingthe load capacity. The number of pairs of recesses 24 and segments 22may vary from 3 to 36 depending upon the operating conditions. Therecesses forming the surfaces 24 may be obtained by etching, stamping,plating or other manufacturing methods for removing, adding or indentingthin sections of material. As an example of operative dimensions withair as a lubricant, assuming the radius of the bore 26 to be 0.2 inch,radius of inner rim 27 to be 0.3 inch, radius 28 to be 2.8 inches, andradius 29 to be 3.0 inches, the recess depth would be 0.0001 inch for arotational speed of 1,725 revolutions per minute and a load of 4 poundsto be supported.

In Figure 5 the machine is positioned similar to the machine of Figure3, however, a ball-type thrust bearing 30 is provided at the lower endof the rotor 10 for engaging an end of a housing 32, therefore,supporting the rotor in the vertical position. A seal 34 is disposedbetween the housing 32 and the shaft 12 in order to prevent the ingressof dirt which would be detrimental to fthe operation of the motor if thecontamination were to enter the space between the rotor and the stator14. Y The dynamoelectric machine of Figure 6 includes the ball-typethrust bearing 30 for positioning the rotor in one direction and a:flange portion 20 on the housing 32. The flange portion 20 has an innersurface which co- .operates with the end surface of the rotor 10 toproduce a hydrodynamic load supporting film as required to 'absorb theend thrust of the rotor. The end of the rotor is modified as indicatedin Figure 4. Here again the modifications of Figure 4 may be applied tothe iiange lwhile Ithe rotor end is kept smooth.

In the construction shown in Figure 7, the rotor 10 includes a bore 36concentric to the axis of rotation of the shaft 12. The cylindricalinner surface of the bore 36 having the finish characteristics andprecision previously described for the critical surfaces. The stator 14has a stud 38 rotatably aflixed thereto. The stud 38 has an outersurface concentric to the axis of rota- 'tion of the shaft 12confronting the inner surfaces of fthe rotor 10. The cylindrical outersurface of the stud 38 is formed with the precision previously describedfor the critical surfaces. Upon rotation of the rotor 10 'thelubricating lm of the ambient uid is produced in the clearance betweenthe rotor bore 36 and .the stud 38. 'i The dynamoelectric device ofFigure 8 is similar to the machine of Figure 7 with the exception thatthrust absorbing and sealing elements are provided. The ball- `thrustbearing 30 engages `the stator housing 32 when rthevrotor 10 moves inone direction and the end of the :rotor 10 opposite to the bearing 30and surrounding the bore 36 being configured as shown in Figure 4produces a hydrodynamic film of fluid between the rotor 110 and thestator 14. A seal 34 prevents the entrance of dirt into the assembly.

In Figure 9 the machine construction differs from that inFigure 8 inthat the bore 36 opens away from the shaft 12 and the ball-thrustbearing 30 is disposed be- -tween the inner end of the bore and the endof the stud 38. Axial movement of the rotor 10 is prevented in `theopposite direction by a hydrodynamic film produced between the end ofthe rotor 10 which is modified in vthe'form shown in Figure 4 and theinwardly extending flange 20 on the stator 14. Here again, the modifiedlhydrodynamic surface may be on the stationary, rather ,than on therotating, member.

A"I n Figure `10, the mechanism of Figure 9 is adapted 6 for operationwith the axis of rotation vertical and with a hydrodynamic thrustbearing. The end of the stud 38 within the bore 36 is configured asshown in Figure 4 and produces a hydrodynamic film of fluid between therotor 10 and the stud 38 to support the rotor 10 out of contact with thestud 38 during operation.

When the rotation of the rotor has ceased, the rotor 10 cornes to restagainst the stator and slight rubbing contact occurs during the startingand stopping phases of the operation. To facilitate the starting of themotor and to reduce the possibility of damage to the surfaces betweenwhich the hydrodynamic film is produced, a solid lubricant such asmoylbdenum disulfide is bonded to the surfaces where rubbing may occur,the solid lubricant being in the form of a very thin film. Other solidlubricants may be employed. However, the properties of molybdenumdisulde are well known in that the coeiicient of friction is very low ascompared to other dry substances.

In the operation of the dynamoelectric devices disclosed herein nolubricant of ordinary type is used. This is especiallyl true of the airlubricated devices. The surface is clean and dry at all times and thebonded solid lubricant, if any, functions only during the starting andstopping of the device. The air film produced by the movement of therotor has the necessary pressure characteristics to support the rotorwithout benefit of contact between the parts or with any lubricant otherthan air. Present accelerated tests indicate that a small integral motorand blower made in accordance with the teachings of this disclosure willremain operable after the equivalent of over 75 years of operation eventhough starting and stopping 20 times per day. This is true even thoughno dry lubricant has been applied to the surfaces of test motors tofacilitate starting and stopping. It thus appears that for practicalpurposes a motor made in accordance with the teaching of this inventioneven though the motor operates continuously will last indefinitely withthe only limitation being the life of the insulation of the windings.

As an example of the high efficiency of this motor, coasting tests havebeen conducted to determine how long a motor rotor will continue torotate after the power has been shut off. In commercially availablemotors the period of time for the best motor is 5 seconds with mostmotors coasting from 2 to 4 seconds. Test motors made in accordance withthe teaching of this invention coast for from to 120 seconds or moreeven though rotor inertia is less than with the commercially availablemotors. In these tests shaded-two-pole motors of 117 volt, 60 cycle, 10watt input were compared.

As a specific example of a dynamoelectric machine made in accordancewith this invention, the first model was constructed from a 4 pole, 115volt, 60 cycle, 1550 r.p.m., induction motor. The motor was modified byrmoving the end brackets, bearings and shaft. The rotor outside diameterwas lapped round, and without taper within 0.0001 inch. The diameter ofthe rotor was approximately 1.6600 inches. The effective rotor lengthwas approximately l and 5A; inches and the rotor weight wasapproximately 1.1 pounds. The stator was bored to 1.7500 inches and abronze sleeve, 1.7502 inches in outside diameter, was pressed in. Thebore of this bronze sleeve was then honed to 1.6605 inches in diameter.'I'he hole was round and without taper within plus or minus 0.0001 inch.The total diametral clearance when cold was 0.0005 inch.

The motor ran with the rotor entirely supported by a pneumodynamic filmof ambient air generated between the rotor and the stator sleevesurfaces. No lubrication other than ambient air was provided. This motorcorresponded to the device disclosed in Figure 2.

Although the invention has been described in its preferred form with acertain degree of particularity, it is understood that the presentdisclosure of the preferred form has been made only byway of example andthat numerous changes in the details of construction and the combinationand arrangement of parts may be resorted to Without departing from theAspirit and the scope of the invention as hereinafter claimed.

I claim:

l. A dynamoelectric device having rotor and stator elements relativelyrotatable about a horizontal axis, each of said elements having a smoothcylindrically contoured surface, said surfaces being complementalsubstantially coaxial, and radially spaced at least 0.000050 inch, saidrotor element being totally supported radially by a dynamic lm ofambient uid produced between said surfaces when the device is inoperation.

2. A ydynamoelectric device having rotor and stator elements relativelyrotatable about a horizontal axis, each of said elements having a smoothcylindrically contoured surface, said surfaces being complementalsubstantially coaxial, and radially spaced at least 0.000050 inch, saidrotor element being totally supported radially by ya fluid dynamic filmof ambient gas produced between said surfaces when the device is inoperation, and a thrust bearing carried by one of the elements, thethrust bearing being interactable with the other of the elements tolimit relative axial'displacement of the elements.

3. A dynamoelectric device having rotor and stator elements relativelyrotatable about a horizontal axis, each of said elements having a smoothcylindrically contoured surface, said surfaces being complementalsubstantially coaxial, and radially spaced at least 0.000050 inch, saidrotor element being totally supported radially by a iiuid dynamic filmof ambient gas produced between said surfaces when the device is inoperation, and a uid dynamic thrust bearing and a ball type thrustbearing carried by the elements, said uid dynamic thrust bearing beingdisposed at one end of said rotor, said ball type thrust bearing beingdisposed at the other end of said rotor, said thrust bearings limitingrelative axial displacement of the elements.

4. A dynamoelectric device comprising, a stator ele ment including meansto induce a magnetic field, the sta-tor having a bore formed therein,the stator having a smooth cylindrically contoured surface defining thebore, and -an armature carried in the bore and having a smoothcylindrically contoured outer surface, said surfaces being substantiallycoaxial and being closely spaced and complementa] to define a loadcarrying gas film producing region therebetween, said rotor beingtotally supported radially on a load carrying film of gas in said regionwhen the device is in operation, said gas film being developed by thecoaction of the surfaces when the armature rotates, the gas for saidfilmbeing supplied by the atmosphere ambient to the device, and said gasfilm being disposed at least in part within said magnetic field.

'5. A dynamoelectric device comprising, a stator element including meansVto induce a magnetic field, the stator having a bore formed therein,the stator having a smooth cylindrically contoured surface defining thebore, an armature carried in the bore and having a smooth cylindricallycontoured outer surface, said surfaces be; ing substantially coaxial andbeing closely spaced and complemental to define a load carrying gas filmproducing region therebetween, each of saidV surfaces having a taper notin excess of 0.0001 inch per inch of surface length and per inch ofdiameter and not in excess .of one-quarter of the radial clearancebetween said surfaces, said surfaces each having a nish of atleast 8microinch KMS., saidV armature being totally supported radially on aload carrying filmof Ygas in said region when the device is inoperation,ysaid gas film being developed lby the coactionV of thesurfaces when the armature rotates, .the gas for said film beingsupplied by the atmosphere ambient to the device, and said gas filmbeingdisposed at least in part within said magnetic field.`

. '6. A dynamoelectric device comprising, a stator velement includingmeans to induce a magnetic field, the stator having a bore formedtherein, the stator having a smooth cylindrically contoured surfacedening the bore, va rotor carried `in the bore and having a smoothcylindrically contoured outer surface, said surfaces being substantiallycoaxial and being closely spaced and complemental to define a loadcarrying fluid film producing region therebetween, said fluid filmregion having Yan average radial dimension of from 0.000050 to 0.003inch per inch of rotor surface diameter, said fluid film being disposedat least in part within said magnetic field, and said rotor beingtotally supported radially by a film of ambient fiuid developed in saidregion when the rotor rotates.

7. A dynamoelectric device comprising a rotor elev ment, a statorelement, the elements having smooth complemental coaxial surfacesdefining a gap therebetween, and a magnetic field inducing membercarried by one of the elements, the other of the elements being anarmature element, said elements being relatively rotatable about ahorizontal axis, said gap being disposed at least in part within theinduced magnetic field and being a load carrying fluid dynamic filmproducing region when the device is in operation, and said rotor beingtotally supported radially on a film of ambient uid in said region whenthe device is in operation.

8. A dynamoelectric machine comprising, first and secondrelementstelescoped together and relatively ro tatable about a horizontal axis,the rst element including a magnetic field producing means and thesecond element being an armature at least partially extending into thefield, the outermost of said elements having a bore formed therein, theoutermost element having a surface defining said bore, the innermostelement being disposed in part within said bore, the innermost elementhaving an outer surface concentric with the outermost element surface,and a nonmagnetic sleeve member carried by one `of the elements andhaving inner and outer surfaces, one of the sleeve member surfaces beingin fixed abutment withthe surface of said one element, Vthe other sleevesurface and the surface of said elements being complemental cylin--drically contoured, smooth, surfaces defining a uid dynamic hnproducing region therebetween, said elements being held in radiallyspaced relationship when the device is in operation solely by the filmof fluid generated in said region, the fluid in said region beingsupplied .by the fluid ambient tothe machine.

9. A dynamoelectric machine comprising, first and second relativelyrotatable elements, the first element having first and second ends and abore extending longitudinally from the first end toward the second end,said first element having a projection extending axially into said bore,the projection having a smooth, cylindrically contoured outer surface,the second element having a smooth, cylindrically Vcontoured surfacedefining the peripheralV limits of an internal bore, said second,element 'being disposed atleast in part within said first element boreand telescoped over said projection, `said surfaces being complementaland defining a fluid dynamic film producing region therebetween, one ofsaid elements being totally supported vby a dynamic lm of uid generatedin said region when the device is in operation, the uid in said regionbeing supplied by the fluid ambient to the machine, and magnetic Vfieldproviding means forming part of the machine andVV causing relativerotation of theV 11. The device of -claim 9` wherein the `magnetic fieldprovided bysch means is an alternating current field, where1n theelements pulsate relatively and transversely of the axis of rotationunder the influence of the alternating current field thereby increasingthe pressure in said film, and wherein the uid is a gas.

12. A dynamoelectric machine comprising, a rotor element and a statorelement, one of said elements including alternating current means toproduce an alternating magnetic field, the other of said elements beingan armature element coactable with the magnetic field to producerelative rotation of the elements when the magnetic field is excited,said rotor and stator being relatively rotatable about a horizontalaxis, said rotor and stator each having a cylindrically contouredsurface coaxial with said axis of rotation, said surfaces defining a gasfilm producing region therebetween, said rotor being totally supportedradially on a load carrying gas film developed in said region when thedevice is in operation, and said region being of sufficient dimension topermit the rotor to pulsate transversely to the axis of rotation underthe influence of the alternating magnetic field and thereby increase thepressure of said film.

13. The dynamoelectric device of claim S having a thrust bearing betweenthe rotor and the stator for limiting axial displacement of the rotor inone direction.

14. The dynamoelectric device of claim 13 wherein the thrust bearingcomprises a hydrodynamic bearing.

15. The dynamoelectric device of claim 13 wherein the thrust bearingcomprises a ball rotatably carried by the rotor and engaging the statorat a point substantially on the axis of rotation.

16. A dynamoelectric device comprising a rotor and a stator elementrelatively rotatable about a horizontal axis, one of said elementsincluding means to induce a magnetic field, the stator having a boretherein and a projection having a cylindrically contoured outer surfacedisposed in the bore, the rotor having an axial bore formed therein, therotor being disposed in the stator bore with the cylindrical projectionextending into the rotor bore, the rotor having an inner surfacedefining said bore, the surfaces being complemental and closely spacedto define a fluid dynamic film producing region therebetween the rotorsurface diameter being from 0.000050 to 0.003 inch per inch of diametergreater than the projection diameter, and the rotor being totallysupported radially by a film of ambient fiuid generated in said regionwhen the elements are relatively rotated.

17. A dynamoelectric device having rotor and stator elements relativelyrotatable about a horizontal axis, each of said elements having a smoothcylindrically contoured surface, said surfaces being complemental andsubstantially coaxial, said surfaces being radially spaced from 0.00005to 0.0005 inch per inch of rotor diameter, said rotor element beingtotally supported radially by a pneumodynamic film of ambient airproduced between said surfaces when the device is in operation.

18. A dynamoelectric device having rotor and stator elements relativelyrotatable about a horizontal axis, each of said elements having a smoothcylindrically contoured surface, said surfaces being complemental andsubstantially coaxial, said surfaces being radially spaced from 0.000050to 0.0005 inch per inch of diameter, said rotor element being totallysupported radially by a pneumodynamic film of ambient air producedbetween said surfaces when the device is in operation, and a thrustbearing carried by one of the elements, the thrust bearing beinginteractable with the other of the elements to limit relative axialdisplacement of the elements, said thrust bearing being a pneumodynamicbearing.

l19. A dynamoelectric device comprising a stator element including meansto induce a magnetic field, the stator having a bore formed therein, thestator having a smooth cylindrically contoured surface defining thebore, an armature carried in the bore and having a smooth cylindricallycontoured outer surface, said surfaces being substantially-coaxial andbeing closely spaced and com- `plemental to define a load carrying gashn producing region therebetween, said region having a radial dimensionof from 0.000050 to 0.0005 inch per inch of rotor surface diameter, eachof said surfaces having a taper not in excess of 0.0001 inch per inch ofsurface length and per inch of diameter and not in excess of one-quarterof the radial dimension of said region, said rotor being totallysupported radially on a load carrying film of gas in said region whenthe device is in operation, said gas film being developed by thecoaction of the surfaces when the armature rotates, the gas for saidfilm being supplied by the atmosphere ambient to the device, and saidgas film being disposed at least in part within said magnetic field.

20. A dynamoelectric device comprising a stator element including meansto induce a magnetic field, the stator having a bore formed therein, thestator having a smooth cylindrically contoured surface defining thebore, and a rotor carried in the bore and having a smooth cylindricallycontoured outer surface, each of said surfaces having a finish at leastas smooth as 8 microinch R.M.S., said surfaces being substantiallycoaxial and being closely spaced and complemental to define a loadcarrying gas -film producing region therebetween, said gas film regionhaving an average radial dimension of from 0.000050 to 0.0005 inch perinch of surface diameter, each of said surfaces having a taper not inexcess of 0.0001 inch per inch of surface length and per inch ofdiameter and not in exces of one-quarter of the radial dimension of saidregion, said rotor being totally supported radially on a load carryingfilm of gas in said region when the device is in operation, said gasfilm being developed by the coaction of the surfaces when the rotorrotates, the gas for said fihn being supplied by the ambient atmosphere,and said gas film being disposed at least in part within said magneticfield.

2l. A dynamoelectric device comprising a stator having a bore therein, arotor rotatable in said bore, a nonmagnetic sleeve lining said bore andon a horizontal axis and having a smooth inner surface, the outersurface of said rotor and the inner surface of said sleeve beinguniformly spaced from 0.000050 to 0.0005 inch per inch of rotor surfacediameter, said rotor being totally supported radially on a film of airgenerated in said sleeve when the device is in operation, the air insaid region being supplied by the atmosphere ambient to saiddynamoelectric device.

22. A dynamoelectric device comprising a rotor and a stator elementrelatively rotatable about a horizontal axis, one of said elementsincluding means to induce a magnetic field, the stator having a boretherein and a projection having a cylindrically contoured outer surfacedisposed in the bore, the rotor having an axial bore formed therein, therotor being disposed in the stator bore with the cylindrical projectionextending into the rotor bore, the rotor having an inner surfacedefining said rotor bore, the surfaces being complemental and closelyspaced to define a pneumodynamic film producing region therebetween therotor surface diameter being from 0.000050 to 0.0005 inch per inch ofdiameter greater than the projection diameter, and the rotor beingtotally supported radially by a film of ambient air generated in saidregion when the elements are relatively rotated.

23. A dynamoelectric machine comprising a rotor element and a statorelement, one of said elements including alternating current means toproduce an alternating magnetic field, the other of said elements beingan armature element coactable with the magnetic field to producerelative rotation of the elements when the magnetic field is excited,said rotor and stator being relatively rotatable about a horizontalaxis, said rotor and stator each having a cylindrically contouredsurface coaxial with said axis of rotation, said surfaces defining apneumodynarnic film producing region therebetween, said region having aradial References Cited in the file of this .patent UNITED STATESPATENTS Southgate "6-..-, Dec; 22 19,114

Gailloud -Y. .V. Y.- Oct. 16, 1,956

FOREIGN PAIENTS Sweden Sept. 12, 1950 Great Britain 1 May 17, 1938

